Flying type thin-film magnetic head

ABSTRACT

A flying type thin-film magnetic head includes a write head element with a coil conductor and a yoke, a write current flowing through the coil conductor, an overcoat layer laminated on the write head element, and a heat-block layer formed in the overcoat layer and made of a material with a heat conductivity that is lower than a heat conductivity of the overcoat layer.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a flying type thin-film magnetichead with an inductive write head element.

[0003] 2. Description of the Related Art

[0004] Such flying type thin-film magnetic head is in general formed ona magnetic head slider flying above a magnetic disk surface inoperation. When a write current flows through a coil of the inductivewrite head element, Joule heat will be produced and thus an over coatlayer or a protection layer for covering the write head element willthermally expand to protrude a part of the magnetic head slider.Therefore, in a recent magnetic head slider with a very low flyingheight, its rear edge or trailing edge that will have the largestprotruded amount may come into contact with and crash onto the surfaceof the rotating magnetic disk.

[0005] In order to prevent such head crash from occurring, the followingcountermeasures have been proposed:

[0006] (1) reduction of heat generation by lowering an electricalresistance of coil in the inductive write head element;

[0007] (2) improvement of heat radiation by thinning of an undercoatlayer on the substrate;

[0008] (3) dissipation of heat by forming a metal pattern on theprotection film (Japanese Patent Publication 05-266428-A2);

[0009] (4) forming of recess at the trailing edge of the magnetic headslider (Japanese Patent Publication 07-307070-A2); and

[0010] (5) forming a recess portion on an air bearing surface (ABS) ofthe protection layer of the magnetic head slider (Japanese PatentPublication 04-366408-A2).

[0011] However, any of the proposed countermeasures cannot sufficientlyreduce the protruded amount to satisfy an extremely lower flying heightthat will be required in future and thus further improvement isrequired.

BRIEF SUMMARY OF THE INVENTION

[0012] It is therefore an object of the present invention to provide aflying type thin-film magnetic head applicable to lower flying heightrequirement by resolving the head crash problems due to thermalexpansion.

[0013] According to the present invention, a flying type thin-filmmagnetic head includes a write head element with a coil conductor and ayoke, a write current flowing through the coil conductor, an overcoatlayer laminated on the write head element, and a heat-block layer formedin the overcoat layer and made of a material with a heat conductivitythat is lower than a heat conductivity of the overcoat layer.

[0014] In the overcoat layer, the heat-block layer made of a materialwith a lower heat conductivity lower than that of the overcoat layer isformed or embedded. Thus, heat transmission is well blocked by thisheat-block layer and thus the thermal expansion of the overcoat layernear its trailing edge is prevented to reduce the amount of protrusionof the trailing edge.

[0015] It is preferred that the heat-block layer is formed to cover aregion with an area larger than that of a region on which the coilconductor is formed.

[0016] It is also preferred that the heat-block layer is formed to coverover the coil conductor.

[0017] It is preferred that the heat-block layer is formed in parallelwith a plane on which the coil conductor is formed.

[0018] Preferably, a distance between the heat-block layer and an airbearing surface (ABS) is less than 15 μm, and more preferably less than7.5 μm.

[0019] It is preferred that the thin-film magnetic head further includesa heater coil conductor formed below the heat-block layer for generatingheat when the head is in operation. This heater coil conductor serves toheat the write head element when the element is in operation so that apart of the write head element intentionally protrudes from the ABS inorder to reduce the flying height. In such thin-film magnetic head, heattransmission is well blocked by this heat-block layer and thus thethermal expansion of the overcoat layer near the trailing edge isprevented to reduce the amount of protrusion of the trailing edge.

[0020] It is also preferred that the heat-block layer is made of aresist material.

[0021] It is further preferred that the thin-film magnetic head includesa read head element.

[0022] Further objects and advantages of the present invention will beapparent from the following description of the preferred embodiments ofthe invention as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0023]FIG. 1 is a sectional view schematically illustratingconfiguration of a thin-film magnetic head as a preferred embodimentaccording to the present invention;

[0024]FIG. 2 is an oblique sectional view of the thin-film magnetic headshown in FIG. 1;

[0025]FIG. 3 illustrates protrusion of the ABS of a magnetic head sliderdue to its thermal expansion;

[0026]FIG. 4 is a graph illustrating the simulation result of aprotruded amount from the ABS due to thermal expansion at each positionof the ABS;

[0027]FIG. 5 is a graph illustrating the simulation result of aprotruded amount from the ABS due to thermal expansion at each positionof the ABS when a distance between a top end of a heat-block layer andthe ABS is changed;

[0028]FIG. 6 is a graph illustrating the simulation result of aprotruded amount from the ABS due to thermal expansion at each positionof the ABS when a distance between the heat-block layer and an upperpole layer is changed;

[0029]FIG. 7 is a sectional view schematically illustratingconfiguration of a thin-film magnetic head as another embodimentaccording to the present invention; and

[0030]FIG. 8 is a graph illustrating the simulation result of aprotruded amount from the ABS due to thermal expansion at each positionof the ABS.

DETAILED DESCRIPTION OF THE INVENTION

[0031]FIG. 1 schematically illustrates configuration of a thin-filmmagnetic head as a preferred embodiment according to the presentinvention, and FIG. 2 shows an oblique sectional view thereof. Thethin-film magnetic head in this embodiment is a composite type thin-filmmagnetic head with an inductive write head element and amagnetoresistive effect (MR) read head element laminated with eachother. However, the thin-film magnetic head in this embodiment maycontain only an inductive write head element.

[0032] In these figures, reference numeral 10 denotes a substrate madeof Al—TiC (Al₂O₃—TiC), 11 denotes an undercoat layer or under layerlaminated on the substrate, 12 denotes an insulation layer laminated onthe undercoat layer 11, 13 denotes a lower shield layer formed on theinsulation layer 12, 14 denotes an upper shield layer also served as alower pole layer, 15 denotes an MR layer formed between the lower andupper shield layers 13 and 14 through a shield gap layer 16, 17 denoteslead conductors electrically connected to the MR layer 15, 18 denotes amagnetic gap layer or record gap layer, 19 denotes an upper pole layer,20 denotes an upper pole tip faced to a top end of the lower pole layer14 through the magnetic gap layer 18, 21 denotes a coil conductor with adouble layers structure, 22 denotes an insulation layer that surroundsthe coil conductor 21, 23 denotes an overcoat layer or protection layermade of for example Al₂O₃, formed on the upper pole layer 19 and theinsulation layer 22, and 24 denotes a heat-block layer formed in theovercoat layer 23 in parallel with the a plane on which the coilconductor 21 is formed and made of a material such as a resist material,with a lower heat conductivity than that of this overcoat layer 23,respectively.

[0033] The heat-block layer 24 is formed to cover a region with an arealarger than that of a region on which the coil conductor 21 is formedand that of a region on which the upper pole layer 19 is formed. Thus,the heat-block layer 24 is formed to cover over the coil conductor 21.

[0034] The overcoat layer 23 has a recess at its ABS corner. Thus, asshown in FIG. 1, an edge of its lower stage constitutes the trailingedge 23 a of the magnetic head slider.

[0035] The upper pole tip 20 is magnetically coupled with the upper polelayer 19 and this upper pole layer 19 is magnetically connected with thelower pole layer 14 at its rear so as to constitute a magnetic yoke ofthe inductive write head element.

[0036] In the thin-film magnetic head with the inductive write headelement, Joule heat is generated by write current flowing through thecoil conductor, and the generated heat is transferred to the overcoatlayer formed thereon. According to the prior art, as shown in FIG. 3,when heated, the overcoat layer easily expands due to a high heatconductivity of Al₂O₃, and thus a part of the ABS of the magnetic headslider protrudes from a normal position 30 to an expanded position 30′.Therefore, the trailing edge of the ABS moves from a position 31 to aposition 31′ by a protruded amount P to narrow the space between thetrailing edge and a surface 32 of the magnetic disk from SN to Spcausing head crash to easily occur.

[0037] Contrary to this, according to this embodiment, the heat-blocklayer 24 made of a resist material and provided with the area largerthan that of the coil conductor 21 and that of the upper pole layer 19is formed or embedded in the overcoat layer 23 to cover over these coilconductor 21 and also upper pole layer 19. A heat conductivity of Al₂O₃constituting the overcoat layer 23 is 1 W/mK, whereas a heatconductivity of the resist material constituting the heat-block layer 24is 0.35 W/mK which is greatly lower than the Al₂O₃ heat conductivity.Therefore, heat transmission is well blocked by this heat-block layer 24and thus the thermal expansion of the overcoat layer 23 near thetrailing edge is prevented to reduce the amount of protrusion of thetrailing edge from the ABS.

[0038]FIG. 4 illustrates the simulation result of a protruded amountfrom the ABS due to thermal expansion at each position of the ABS. Inthe figure, a line a represents the protruded amount of the conventionalthin-film head with no heat-block layer, and a line b represents theprotruded amount of the thin-film head with the heat-block layeraccording to this embodiment. The longitudinal axis of this figureindicates the protruded amount (nm), and the lateral axis indicates adistance (μm) along the ABS from a reference position that is defined atthe interface of the substrate 10 and the undercoat layer 11. Theheat-block layer 24 used for simulating the protruded amount has arectangular parallelepiped with a thickness or a height seen from theABS of 1.0 μm, a depth seen from the ABS of 106 μm and a width seen fromthe ABS of 113 μm. Also, the coil conductor 21 has a height of about 55μm and a width of about 70 μm, and located with a space of 6 μm from theABS.

[0039] As will be noted from comparison of the lines a and b, thethin-film magnetic head according to this embodiment can reduce theprotruded amount near the trailing edge by about 0.3 nm, and thuspossibility of contact or crash of the trailing edge onto the magneticdisk surface can be remarkably decreased even for a low-flying heightthin-film magnetic head.

[0040]FIG. 5 illustrates the simulation result of a protruded amountfrom the ABS due to thermal expansion at each position of the ABS when adistance between a top end of the heat-block layer 24 and the ABS ischanged. In the figure, a line A represents the protruded amount of theconventional thin-film head with no heat-block layer, and lines B to Erepresent the protruded amount of the thin-film head with the heat-blocklayer according to this embodiment. The distances between the top end ofthe heat-block layer and the ABS in the heads of lines B, C, D and E are3 μm, 5 μm, 15 μm and 25 μm, respectively. The longitudinal axis of thisfigure indicates the protruded amount (nm), and the lateral axisindicates a distance (μm) along the ABS from a reference position thatis defined at the interface of the substrate 10 and the undercoat layer11.

[0041] As will be noted from the figure, if the distance between the topend of the heat-block layer 24 and the ABS is less than 15 μm, theprotruded amount near the trailing edge becomes lower than that in theconventional thin-film magnetic head, and thus possibility of contact orcrash of the trailing edge onto the magnetic disk surface can bedecreased even for a low-flying height thin-film magnetic head. If thedistance between the top end of the heat-block layer 24 and the ABS isless than 5 μm, more desired result is obtained.

[0042]FIG. 6 illustrates the simulation result of a protruded amountfrom the ABS due to thermal expansion at each position of the ABS when adistance between the heat-block layer 24 and the upper pole layer 19 ischanged. In the figure, a line (a) represents the protruded amount ofthe conventional thin-film head with no heat-block layer, and lines (b)to (e) represent the protruded amount of the thin-film head with theheat-block layer according to this embodiment. The distances between theheat-block layer 24 and the upper pole layer 19 in the heads of lines(b), (c), (d) and (e) are 2 μm, 2.5 μm, 5.5 μm and 7.5 μm, respectively.The longitudinal axis of this figure indicates the protruded amount(nm), and the lateral axis indicates a distance (μm) along the ABS froma reference position that is defined at the interface of the substrate10 and the undercoat layer 11.

[0043] As will be noted from the figure, if the distance between the topend of the heat-block layer 24 and the upper pole layer 19 is less than7.5 μm, the protruded amount near the trailing edge becomes lower thanthat in the conventional thin-film magnetic head, and thus possibilityof contact or crash of the trailing edge onto the magnetic disk surfacecan be decreased even for a low-flying height thin-film magnetic head.If the distance between the top end of the heat-block layer 24 and theupper pole layer 19 is 2.5-5.5 μm, more desired result is obtained.

[0044]FIG. 7 schematically illustrates configuration of a thin-filmmagnetic head as another embodiment according to the present invention.The thin-film magnetic head in this embodiment is a composite typethin-film magnetic head with an inductive write head element and an MRread head element laminated with each other. However, the thin-filmmagnetic head in this embodiment may contain only an inductive writehead element.

[0045] In the figure, reference numeral 70 denotes a substrate made ofAl—TiC (Al₂O₃—TiC), 71 denotes an undercoat layer or under layerlaminated on the substrate, 72 denotes an insulation layer laminated onthe undercoat layer 71, 73 denotes a lower shield layer formed on theinsulation layer 72, 74 denotes an upper shield layer also served as alower pole layer, 75 denotes an MR layer formed between the lower andupper shield layers 73 and 74 through a shield gap layer 76, 77 denoteslead conductors electrically connected to the MR layer 75, 78 denotes amagnetic gap layer or record gap layer, 79 denotes an upper pole layer,80 denotes an upper pole tip faced to a top end of the lower pole layer74 through the magnetic gap layer 78, 81 denotes a coil conductor with adouble layers structure, 82 denotes an insulation layer that surroundsthe coil conductor 81, 83 denotes an overcoat layer or protection layermade of for example Al₂O₃, formed on the upper pole layer 79 and theinsulation layer 82, and 84 denotes a heat-block layer formed in theovercoat layer 83 in parallel with the a plane on which the coilconductor 81 is formed and made of a material such as a resist material,with a lower heat conductivity than that of this overcoat layer 83,respectively.

[0046] The heat-block layer 84 is formed to cover a region with an arealarger than that of a region on which the coil conductor 81 is formedand that of a region on which the upper pole layer 79 is formed. Thus,the heat-block layer 84 is formed to cover over the coil conductor 81.

[0047] An area of the heat-block layer 84 is larger than that of thecoil conductor 81 and also that of the upper pole layer 79.

[0048] The overcoat layer 83 has a recess at its ABS corner. Thus, asshown in FIG. 7, an edge of its lower stage constitutes the trailingedge 83 a of the magnetic head slider.

[0049] The upper pole tip 80 is magnetically coupled with the upper polelayer 79 and this upper pole layer 79 is magnetically connected with thelower pole layer 74 at its rear so as to constitute a magnetic yoke ofthe inductive write head element.

[0050] According to this embodiment, in particular, a heater coilconductor 85 is formed or embedded in the undercoat layer 71 formedbelow the heat-block layer 83. This heater coil conductor 85 serves toheat the write head element and/or the read head element when writeand/or read operations so that a part of the write head element and/orthe read head element intentionally protrudes from the ABS in order toreduce the flying height.

[0051] Not only heat from this heat coil conductor 85 but also Jouleheat generated by write current flowing through the coil conductor 81may be transferred to the overcoat layer 83 formed thereon. However,according to this embodiment, the heat-block layer 84 made of a resistmaterial and provided with a larger area than that of the coil conductor81 and the upper pole layer 79 is formed or embedded in the overcoatlayer 83 to cover over these coil conductor 81 and upper pole layer 79.A heat conductivity of Al₂O₃ constituting the overcoat layer 83 is 1W/mK, whereas a heat conductivity of the resist material constitutingthe heat-block layer 84 is 0.35 W/mK which is greatly lower than theAl₂O₃ heat conductivity. Therefore, heat transmission is well blocked bythis heat-block layer 84 and thus the thermal expansion of the overcoatlayer 83 near the trailing edge is prevented to reduce the amount ofprotrusion of the trailing edge from the ABS.

[0052]FIG. 8 illustrates the simulation result of a protruded amountfrom the ABS due to thermal expansion at each position of the ABS. Inthe figure, a line (A) represents the protruded amount of theconventional thin-film head with no heat-block layer, and a line (B)represents the protruded amount of the thin-film head with theheat-block layer according to this embodiment. The longitudinal axis ofthis figure indicates the protruded amount (nm), and the lateral axisindicates a distance (μm) along the ABS from a reference position thatis defined at the interface of the substrate 70 and the undercoat layer71. The heat-block layer 84 used for simulating the protruded amount hasa rectangular parallelepiped with a thickness or a height seen from theABS of 1.0 μm, a depth seen from the ABS of 106 μm and a width seen fromthe ABS of 113 μm. Also, the coil conductor 81 has a height of about 55μm and a width of about 70 μm, and located with a space of 6 μm from theABS.

[0053] As will be noted from comparison of the lines (A) and (B), thethin-film magnetic head according to this embodiment can reduce theprotruded amount near the trailing edge by about 2.0 nm, and thuspossibility of contact or crash of the trailing edge onto the magneticdisk surface can be remarkably decreased even for a low-flying heightthin-film magnetic head with the heater coil.

[0054] Many widely different embodiments of the present invention may beconstructed without departing from the spirit and scope of the presentinvention. It should be understood that the present invention is notlimited to the specific embodiments described in the specification,except as defined in the appended claims.

1. A flying type thin-film magnetic head comprising: a write headelement with a coil conductor and a yoke, a write current flowingthrough said coil conductor; an overcoat layer laminated on said writehead element; and a heat-block layer formed in said overcoat layer andmade of a material with a heat conductivity that is lower than a heatconductivity of said overcoat layer.
 2. The thin-film magnetic head asclaimed in claim 1, wherein said heat-block layer is formed to cover aregion with an area larger than that of a region on which said coilconductor is formed.
 3. The thin-film magnetic head as claimed in claim1, wherein said heat-block layer is formed to cover over said coilconductor.
 4. The thin-film magnetic head as claimed in claim 1, whereinsaid heat-block layer is formed in parallel with a plane on which saidcoil conductor is formed.
 5. The thin-film magnetic head as claimed inclaim 1, wherein a distance between said heat-block layer and an airbearing surface is less than 15 μm.
 6. The thin-film magnetic head asclaimed in claim 1, wherein a distance between said heat-block layer andan air bearing surface is less than 7.5 μm.
 7. The thin-film magnetichead as claimed in claim 1, wherein said thin-film magnetic head furthercomprises a heater coil conductor formed below said heat-block layer forgenerating heat when said head is in operation.
 8. The thin-filmmagnetic head as claimed in claim 1, wherein said heat-block layer ismade of a resist material.
 9. The thin-film magnetic head as claimed inclaim 1, wherein said thin-film magnetic head further comprises a readhead element.